LGR for script: Thaana (Thaa) | rz-lgr-6-thaana-script-23sep25-en

This document is mechanically formatted from the above XML file for the LGR. It provides additional summary data and explanatory text. The XML file remains the sole normative specification of the LGR.

Date | 2025-09-23
LGR Version | 6 (Root Zone LGR for the Thaana Script)
Language | und-Thaa (Thaana Script)
Unicode Version | 16.0.0

# Description

# Root Zone Label Generation Rules for the Thaana Script

## Overview

This file contains a set of Label Generation Rules (LGR) for the Thaana script for the Root Zone. For more details on this LGR and additional background on the script, see “Proposal for a Thaana Script Root Zone LGR” [Proposal-Thaana]. This file is one of a set of LGR files that together form an integrated LGR for the DNS Root Zone [RZ-LGR-6]. The format of this file follows [RFC 7940].

## Repertoire

The repertoire includes the 36 letters and diacritics of the Thaana script in everyday use as defined in Section 5.1 “Included Code Points” in [Proposal-Thaana].

U+07B1 ޱ THAANA LETTER NAA (baru noonu, heavy n) is a dialect specific consonant. Given the resurgence of the use of the consonant in online writing and social media, a decision was made to include it in the repertoire at this time, despite it not being officially recognized as part of the base consonants.

The Thaana script contains a series of consonants used for writing Arabic loan words. Their occurrence is relatively rare and omitting them here avoids some complications that might make their use problematic for the Root Zone. The primary issue is that they are used inconsistently and alternation with the equivalent ordinary consonants is common. Their inclusion would thus have necessitated the definition of in-script variants. See also Section 5.2 “Excluded Code Points” in [Proposal-Thaana]

As part of the Root Zone, this LGR includes neither decimal digits nor the HYPHEN-MINUS.

Repertoire Listing: Each code point or range is tagged with the script or scripts with which the code point is used and one or more other character categories. For each repertoire element, one or more references document sufficient justification for inclusion in the repertoire; see the “References” below.

## Variants

This LGR defines one set of in-script variants as described in Section 6.1 “In-script Variants”of [Proposal-Thaana]. No cross-script variants have been identified based on any discernable similarity with another script or otherwise required for the security of the Thaana LGR. In particular, the structure of the Thaana script, requiring a vowel after each consonant, removes similarity between Arabic and Thaana labels.

Variant Disposition: All variants are of type “blocked”, making labels that differ only by these variants mutually exclusive: whichever label containing either of these variants is chosen earlier would be delegated, while any other equivalent labels should be blocked. There is no preference among these labels.

This LGR does not define allocatable variants.

The specification of variants in the Root Zone LGR follows the guidelines in [RFC 8228].

## Character Classes

Thaana has 25 consonants and 11 vowels. The vowels are written above/below the letters.

- Consonants — in the Thaana script, consonants are base characters and must be followed by a vowel.
- Vowels — vowels are combining marks that always follow a consonant.

## Whole Label Evaluation (WLE) and Context Rules

### Default Whole Label Evaluation Rules and Actions

The LGR includes the set of required default WLE rules and actions applicable to the Root Zone and defined in [MSR-6]. They are marked with ⍟. The actions compute a label disposition based on WLE rules or variant mapping types.

### Script-specific Rules

The LGR defines the following script-specific rules concerning the placement of consonants and vowels.

- follows-C — WLE 1: a vowel always follows a consonant including Noonu and Raa.
- followed-by-V — WLE 2: a consonant, including Noonu or Raa is always followed by a vowel.

Note that in writing Thaana, U+0782 ނ THAANA LETTER NOONU and U+0783 ރ THAANA LETTER RAA can either appear with or without a vowel, depending on the context. For the purpose of the Root Zone, these special contexts have been disallowed and they behave like all other consonants for the purpose of the RZ-LGR. Because the exceptions to their behavior as ordinary consonants are statistically rare, this more conservative approach was chosen even though it restricts a small number of labels that might be valid in other zones.

## Methodology and Contributors

The Root Zone LGR for the Thaana Script was developed by the Thaana Generation Panel. For details on methodology and contributors, see Sections 4 and 8 in [Proposal-Thaana], as well as [RZ-LGR-6-Overview].

## References

This document cites the following general references.

[MSR-6]
  Integration Panel, “Maximal Starting Repertoire — MSR-6 Overview and Rationale”, 23 September 2025,
  https://www.icann.org/en/system/files/files/msr-6-overview-23sep25-en.pdf
[Proposal-Thaana]
  “Thaana Script Label Generation Rules for the Root Zone” , 23 May 2025,
  https://www.icann.org/en/system/files/files/proposal-thaana-lgr-23may25-en.pdf
[RFC 7940]
  Davies, K. and A. Freytag, “Representing Label Generation Rulesets Using XML”, RFC 7940, August 2016,
  https://www.rfc-editor.org/info/rfc7940
[RFC 8228]
  A. Freytag, “Guidance on Designing Label Generation Rulesets (LGRs) Supporting Variant Labels”, RFC 8228, August 2017,
  https://www.rfc-editor.org/info/rfc8228
[RZ-LGR-6-Overview]
  Integration Panel, “Root Zone Label Generation Rules (RZ LGR-6): Overview and Summary”, 23 September 2025,
  https://www.icann.org/sites/default/files/lgr/rz-lgr-6-overview-23sep25-en.pdf
[RZ-LGR-6]
  Integration Panel, “Root Zone Label Generation Rules (RZ-LGR-6)”, 23 September 2025 (XML),
  https://www.icann.org/sites/default/files/lgr/rz-lgr-6-common-23sep25-en.xml
  non-normative HTML presentation:
  https://www.icann.org/sites/default/files/lgr/rz-lgr-6-common-23sep25-en.html
[Unicode 16.0.0]
  The Unicode Consortium. The Unicode Standard, Version 16.0.0, (South San Francisco: The Unicode Consortium, 2024. ISBN 978-1-936213-34-4)
  https://www.unicode.org/versions/Unicode16.0.0/

References [0] to [3] refer to the Unicode Standard versions in which the corresponding code points were initially encoded. References [401] and above correspond to sources given in [Proposal-Thaana] justifying the inclusion of the corresponding code points.

# Repertoire

## Repertoire Summary

Number of elements in repertoire | 36
Longest code point sequence | 1

## Repertoire by Code Point

The following table lists the repertoire by code point (or code point sequence). The data in the Script and Name column are extracted from the Unicode character database. Where a comment in the original LGR is equal to the character name, it has been suppressed.

For any code point or sequence for which a variant is defined, additional information is provided in the Variants column. See also the legend provided below the table.

Code Point | Glyph | Script | Name | Ref | Tags | Required Context | Variants | Comment
--- | --- | --- | --- | --- | --- | --- | --- | ---
U+0780 | ހ | Thaana | THAANA LETTER HAA | [3], [401], [402] | consonant | followed-by-V |  |
U+0781 | ށ | Thaana | THAANA LETTER SHAVIYANI | [3], [401], [402] | consonant | followed-by-V |  |
U+0782 | ނ | Thaana | THAANA LETTER NOONU | [3], [401], [402] | consonant | followed-by-V | set 1 | Behaves like any other consonant for Root Zone labels
U+0783 | ރ | Thaana | THAANA LETTER RAA | [3], [401], [402] | consonant | followed-by-V |  | Behaves like any other consonant for Root Zone labels
U+0784 | ބ | Thaana | THAANA LETTER BAA | [3], [401], [402] | consonant | followed-by-V |  |
U+0785 | ޅ | Thaana | THAANA LETTER LHAVIYANI | [3], [401], [402] | consonant | followed-by-V |  |
U+0786 | ކ | Thaana | THAANA LETTER KAAFU | [3], [401], [402] | consonant | followed-by-V |  |
U+0787 | އ | Thaana | THAANA LETTER ALIFU | [3], [401], [402] | consonant | followed-by-V |  |
U+0788 | ވ | Thaana | THAANA LETTER VAAVU | [3], [401], [402] | consonant | followed-by-V |  |
U+0789 | މ | Thaana | THAANA LETTER MEEMU | [3], [401], [402] | consonant | followed-by-V |  |
U+078A | ފ | Thaana | THAANA LETTER FAAFU | [3], [401], [402] | consonant | followed-by-V |  |
U+078B | ދ | Thaana | THAANA LETTER DHAALU | [3], [401], [402] | consonant | followed-by-V |  |
U+078C | ތ | Thaana | THAANA LETTER THAA | [3], [401], [402] | consonant | followed-by-V |  |
U+078D | ލ | Thaana | THAANA LETTER LAAMU | [3], [401], [402] | consonant | followed-by-V |  |
U+078E | ގ | Thaana | THAANA LETTER GAAFU | [3], [401], [402] | consonant | followed-by-V |  |
U+078F | ޏ | Thaana | THAANA LETTER GNAVIYANI | [3], [401], [402] | consonant | followed-by-V |  |
U+0790 | ސ | Thaana | THAANA LETTER SEENU | [3], [401], [402] | consonant | followed-by-V |  |
U+0791 | ޑ | Thaana | THAANA LETTER DAVIYANI | [3], [401], [402] | consonant | followed-by-V |  |
U+0792 | ޒ | Thaana | THAANA LETTER ZAVIYANI | [3], [401], [402] | consonant | followed-by-V |  |
U+0793 | ޓ | Thaana | THAANA LETTER TAVIYANI | [3], [401], [402] | consonant | followed-by-V |  |
U+0794 | ޔ | Thaana | THAANA LETTER YAA | [3], [401], [402] | consonant | followed-by-V |  |
U+0795 | ޕ | Thaana | THAANA LETTER PAVIYANI | [3], [401], [402] | consonant | followed-by-V |  |
U+0796 | ޖ | Thaana | THAANA LETTER JAVIYANI | [3], [401], [402] | consonant | followed-by-V |  |
U+0797 | ޗ | Thaana | THAANA LETTER CHAVIYANI | [3], [401], [402] | consonant | followed-by-V |  |
U+07A6 | ަ | Thaana | THAANA ABAFILI | [3], [401], [402] | vowel | follows-C |  |
U+07A7 | ާ | Thaana | THAANA AABAAFILI | [3], [401], [402] | vowel | follows-C |  |
U+07A8 | ި | Thaana | THAANA IBIFILI | [3], [401], [402] | vowel | follows-C |  |
U+07A9 | ީ | Thaana | THAANA EEBEEFILI | [3], [401], [402] | vowel | follows-C |  |
U+07AA | ު | Thaana | THAANA UBUFILI | [3], [401], [402] | vowel | follows-C |  |
U+07AB | ޫ | Thaana | THAANA OOBOOFILI | [3], [401], [402] | vowel | follows-C |  |
U+07AC | ެ | Thaana | THAANA EBEFILI | [3], [401], [402] | vowel | follows-C |  |
U+07AD | ޭ | Thaana | THAANA EYBEYFILI | [3], [401], [402] | vowel | follows-C |  |
U+07AE | ޮ | Thaana | THAANA OBOFILI | [3], [401], [402] | vowel | follows-C |  |
U+07AF | ޯ | Thaana | THAANA OABOAFILI | [3], [401], [402] | vowel | follows-C |  |
U+07B0 | ް | Thaana | THAANA SUKUN | [3], [401], [402] | vowel | follows-C |  |
U+07B1 | ޱ | Thaana | THAANA LETTER NAA | [5], [401], [402] | consonant | followed-by-V | set 1 |

Legend

Code Point
  A code point or code point sequence.
Glyph
  The shape displayed depends on the fonts available to your browser.
Script
  Shows the script property value from the Unicode Character Database. Combining marks may have the value Inherited and code points used with more than one script may have the value Common.
Name
  Shows the character or sequence name from the Unicode Character Database.
Ref
  Links to the references associated with the code point or sequence, if any.
Tags
  LGR-defined tag values. Any tags matching the Unicode script property are suppressed in this view.
Required Context
  Link to a rule defining the required context a code point or sequence must satisfy. If prefixed by “not:” identifies a context that must not occur.
Variants
  Link to the variant set the code point or sequence is a member of, except where a coded point or sequence maps only to itself, in which case the type of that mapping is listed.
Comment
  The comment as given in the XML file. However, if the comment for this row consists only of the code point or sequence name, it is suppressed in this view. By convention, comments starting with “=” denote an alias. If present, the symbol ⍟ marks a default item shared among a set of LGRs.

# Variants

## Variant Set Summary

Number of variant sets | 1
Largest variant set | 2
Variants by Type |
blocked | 2

## Variant Sets

The following tables list all variant sets defined in this LGR, except for singleton sets. Each table lists all variant mapping pairs of the set; one per row. Mappings are assumed to be symmetric: each row documents both forward (→) and reverse (←) mapping directions. In each table, the mappings are sorted by Source value in ascending code point order; shading is used to group mappings from the same source code point or sequence.

Where the type of both forward and reverse mappings are the same, a single value is given in the Type column; otherwise the types for forward and reverse mappings, as well as comments and references, are listed above one another. For summary counts, both forward and reverse mappings are always counted separately.

In any LGR with variant specifications that are well behaved, all members within each variant set are defined as variants of each other; the mappings in each set are symmetric and transitive; and all variant sets are disjoint.

Common Legend

Source
  By convention, the smaller of the two code points in a variant mapping pair.
Target
  By convention, the larger of the two code points in a variant mapping pair.
Glyph
  The shape displayed for source or target depends on the fonts available to your browser.
→ - forward
  Indicates that Type, Ref and Comment apply to the mapping from source to target.
← - reverse
  Indicates that Type, Ref and Comment apply to the reverse mapping from target to source.
↔ - both
  Indicates that Type, Ref and Comment apply to both forward and reverse mapping.
Type
  The type of the variant mapping, including predefined variant types such as “allocatable” and “blocked”; or any that are defined specifically for this LGR.
Ref
  One or more reference IDs (optional). A “/” separates references for reverse / forward mappings, if different.
Comment
  A descriptive comment (optional). A “/” separates comments for reverse / forward mappings, if different.

### Variant Set 1 — 2 Members

Source | Glyph | Target | Glyph |  | Type | Ref | Comment
--- | --- | --- | --- | --- | --- | --- | ---
0782 | ނ | 07B1 | ޱ | ↔ | blocked |  |

# Classes, Rules and Actions

## Character Classes

Number of named classes | 2
Implicit defined by script tag | 1

The following table lists all named and implicit classes with their definition and a list of their members intersected with the current repertoire (for larger classes, this list is elided).

Name | Definition | Count | Members or Ranges | Ref | Comment
--- | --- | --- | --- | --- | ---
C | Tag=consonant | 25 | {0780-0797 07B1} |  | Any Thaana consonant including Noonu and Raa
V | Tag=vowel | 11 | {07A6-07B0} |  | Any Thaana vowel
implicit | Tag=sc:Thaa | 36 | {0780-0797 07A6-07B1} |  | Any character tagged as Thaana

Legend

Members or Ranges
  Lists the members of the class as code points (xxx) or as ranges of code points (xxx-yyy). Any class too numerous to list in full is elided with "...".
Tag=ttt
  A named or implicit class defined by all code points that share the given tag value (ttt).
Implicit
  An anonymous class implicitly defined based on tag value and for which there is no named equivalent.

## Whole Label Evaluation and Context Rules

Number of rules | 3
Used to trigger actions | 1
Used as context rule (C) | 2
Anchored context rules | 2

The following table lists all named rules defined in the LGR and indicates whether they are used as trigger in an action or as context (when or not-when) for a code point or variant.

Name | Regular Expression | Used as Trigger | Anchor | Used as Context | Ref | Comment
--- | --- | --- | --- | --- | --- | ---
leading-combining-mark | `(start)[\p{gc=Mn}][\p{gc=Mc}]` | ✔ |  |  |  | Default WLE rule matching labels with leading combining marks ⍟
follows-C | `([:C:])← ⚓︎` |  | ✔ | C |  | WLE1: a vowel always follows a consonant.
followed-by-V | `⚓︎ →([:V:])` |  | ✔ | C |  | WLE2: a consonant is always followed by a vowel.

Legend

Used as Trigger
  This rule triggers one of the actions listed below.
Used as Context
  This rule defines a required or prohibited context for a code point C or variant V.
Anchor
  This rule has a placeholder for the code point for which it is evaluated.
Regular Expression
  A regular expression equivalent to the rule, shown in a modified notation as noted:
⚓︎ - context anchor
  Placeholder for the actual code point when a context is evaluated. The code point must occur at the position corresponding to the anchor. Rules containing an anchor cannot be used as triggers.
(...)← - look-behind
  If present encloses required context preceding the anchor.
→(..) - look-ahead
  If present encloses required context following the anchor.
start or end
  (start) matches the start of the label; (end) matches the end of the label.
[: :] - named or implicit character set
  Reference to a named character set [:name:] or an implicit character set [:tag:]. A leading “^” before name or tag indicates the set complement.
[\p{ }] - property
  Set of all characters matching a given value for a Unicode property [\p{prop=val}]. Note: uppercase “\P” defines the complement of a property set.
∅= - empty set
  Indicates that the following set is empty because of the result of set operations, or because none of its elements is part of the repertoire defined here. A rule with a non-optional empty set never matches.
⍟ - default rule
  Rules marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

## Actions

The following table lists the actions that are used to assign dispositions to labels and variant labels based on the specified conditions. The order of actions defines their precedence: the first action triggered by a label is the one defining its disposition.

# | Condition | Rule / Variant Set |  | Disposition | Ref | Comment
--- | --- | --- | --- | --- | --- | ---
1 | if label matches | leading-combining-mark | → | invalid |  | labels with leading combining marks are invalid ⍟
2 | if at least one variant is in | {out-of-repertoire-var} | → | invalid |  | any variant label with a code point out of repertoire is invalid ⍟
3 | if at least one variant is in | {blocked} | → | blocked |  | any variant label containing blocked variants is blocked ⍟
4 | if each variant is in | {allocatable} | → | allocatable |  | variant labels with all variants allocatable are allocatable ⍟
5 | if any label (catch-all) |  | → | valid |  | catch all (default action) ⍟

Legend

{...} - variant type set
  In the “Rule/Variant Set” column, the notation {...} means a set of variant types.
⍟ - default action
  Actions marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

Note: The following variant types are used in one or more actions, but are not defined in this LGR: allocatable, out-of-repertoire-var. This is not necessarily an error.

# Table of References

The following lists the references cited for specific code points, variants, classes, rules or actions in this LGR. For General references refer to the References section in the Description.

[0] | The Unicode Standard, Version 1.1 Any code point originally encoded in Unicode Version 1.1
[3] | The Unicode Standard, Version 3.0 Any code point originally encoded in Unicode Version 3.0
[5] | The Unicode Standard, Version 3.2 Any code point originally encoded in Unicode Version 3.2
[401] | Dhivehi Writing Systems by Naseema Mohamed, page 7-8, NCLHR, 1999.
[402] | Maldivian (ދިވެހި), Omniglot, https://www.omniglot.com/writing/thaana.htm (Accessed on 5 February 2025)